Member arranged to act between two in relation to each other movable parts of a vehicle

ABSTRACT

The present invention relates to a member ( 1 ) arranged to act between two parts of a vehicle which are movable in relation to each other. The member ( 1 ) comprises a first portion ( 2 ) having an elongated rod ( 6 ) with external threads ( 7 ) and a second portion ( 3 ) having a nut ( 8 ) rotatably provided on the rod ( 6 ) so that the length of the member ( 1 ) during a rotary motion between the rod ( 6 ) and nut ( 8 ) is variable in an axial direction (L). An electric rotor machine ( 10 ), having a stator ( 11 ) and a rotor ( 13 ) which is rigidly connected to said nut ( 8 ), is arranged to influence said rotary motion. The rotor ( 13 ) and nut ( 18 ) are so positioned in relation to each other that at least a radial plane with respect to the axial direction (L) extends both through the rotor ( 13 ) and the nut ( 8 ).

TECHNICAL FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a member arranged to act between twoparts of a vehicle which are movable in relation to each other, whereinthe member extends between said parts and comprises a first portionconnectable to the first part of the vehicle and a second portionconnectable to the second part of the vehicle, wherein the first portioncomprises an elongated rod having external threads and the secondportion a nut provided rotatably on the rod so that the length of themember, during a rotary motion between the rod and the nut, is variablein an axial direction, wherein an electric rotor machine having a statorand a rotor is arranged to influence said rotary motion and wherein therotor and the nut are so located in relation to each other that at leastone radial plane with respect to the axial direction extends boththrough the rotor and the nut.

In order to obtain a good comfort for passengers in a trackboundvehicle, it is usually equipped with members arranged to damp themotions of a car body in relation to an underlying bogie frame. Inmodern trackbound vehicles, members are also used which are arranged todisplace the car body laterally in relation to the underlying bogieframe during travel in curves and also to tilt the car body for thepurpose of further increasing the travel comfort for the passengers.Usually, such members are hydraulic or pneumatic. A disadvantage withthe hydraulic or pneumatic members is that they are subject to faultsand that they require a great deal of maintenance.

From DE 296 21 247 01 it is known to arrange an electrically drivenmember in a trackbound vehicle in order to control the tilting of thecar body during travel in curves. The member is attachable between thecar body and an underlying bogie frame and comprises two in relation toeach other in the longitudinal direction displaceable portions. Thefirst portion comprises a nut and the second portion an elongatedthreaded rod, which during rotation co-operates with the nut so that thelength of the member may be changed. The second portion comprises forthe rotation of the rod, an electric rotor machine having a stator and arotor rigidly connected to the rod. The alternative possibility that theelectric rotor machine may drive the nut instead of the rod is alsoindicated in the document.

In order for an electric rotor machine to be able to displace a car bodyin relation to a bogie frame without deteriorating the dynamicproperties of the trackbound vehicle, the parts rotating with the rotormay not have a too large momentum of inertia. Therefore, the mass ofsaid rotating parts ought to be as small as possible. A disadvantagewith the known construction is that the motions of the rotor aretransferred to the rod, which has a relatively large mass. Furthermore,the transmission between the rotor and the rod occurs at a firstposition whereafter the rotary motion of the rod is transferred to thenut at a second position located at a distance from the first position.Such a transmission comprises a considerable amount of losses.Therefore, the known electric member described above will presumably notfunction well in order to displace a car body.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an electric drivenmember of the initially mentioned kind which has a relatively small andcompact construction and which may act between vehicle parts of aconsiderable weight in a reliable way. Thereby, such an electric membermay replace conventional hydraulic and pneumatic members.

This object is achieved by said member initially mentioned, which ischaracterised in that the rotor and nut are rigidly connected andconstitute an integrated part. Thereby, no separate coupling devicebetween the rotor and the nut needs to be provided and the losses ofthis power transmission are thereby nearly non-existent. Furthermore, avery short power transmission path is obtained for the transmission ofthe rotary motion of the rotor, via the nut, to the rod and vice versa.An electric member according the above may therefore be manufactured asa compact construction with few parts. Therefore, the member may alsobecause of its simplicity be manufactured with a low cost. Furthermore,such a member is substantially cheaper in operation than conventionalhydraulic and pneumatic members since it requires less maintenance.

According to a preferred embodiment of the invention, the nut comprisesinternally carried balls arranged to run along the external threads ofthe rod during the rotary motion of the nut. With such balls it isachieved that the friction between the nut and the rod during the rotarymotion is very low at the same time as the balls allow a certaininclination of the rod in relation to the nut without any appreciableincrease of the friction therebetween.

According to another preferred embodiment of the invention, the statoris rigidly connected to the second portion. Thereby, the second portionmay have an inner cavity suited to receive the electric rotor machinewhose stator, which usually has an external cylindrical-shape, isrigidly attached in said cavity in a suitable way.

According to another preferred embodiment of the invention, the electricrotor machine is arranged to displace said vehicle parts in relation toeach other via the member, when needed. The member may thereby becoupled to a control unit, which, for example, senses the lateralacceleration of the vehicle and the mutual position of the vehicleparts, the direction of motion and the velocity. Depending on saidsensed values, the control unit may initiate a displacement of saidvehicle parts to a desired position by means of a suitable supply ofenergy to the electric rotor machine. The electric rotor machine mayalso be arranged to damp the motions between the vehicle parts via themember, when needed. Such a member may thereby replace conventionaldamper members of the hydraulic or the pneumatic type. Such members maytherewith work as displacement members or damper members on, mostpreferably, both as displacement members and damper members.

According to another preferred embodiment of the invention, the electricrotor machine comprises a permanently magnetised synchronous motor. Inthis case, the rotor is permanently magnetised and will thereby rotateexactly with the rotation speed of the rotating magnetic field. Therotation speed of the rotor is decided by the current frequency in thestator windings and the number of poles. By such an electric rotormachine, it is easy to give the member a necessary control and therebysuch properties that it becomes suitable as displacement member anddamper member. Other types of electric rotor machines than a permanentlymagnetised synchronous motor are also possible to use in order to obtainsaid displacement and/or damping.

According to another preferred embodiment of the invention, the vehicleis a trackbound vehicle. In trackbound vehicles, the supply of electricenergy is usually not a problem and it is usually an advantage to beable to replace hydraulic or pneumatic members by electric ones. This isdue to the fact that the electric driven members with auxiliaryequipment require substantially less maintenance than the hydraulic orpneumatic ones. Furthermore, they require less space and have asubstantially lower weight. Advantageously, said first and second partsof the vehicle are a car body and a bogie frame. In trackbound vehiclessuch a member may mostly be intended to influence the motions of the carbody, in order to improve the travel comfort for the passengers. Themember may thereby be arranged to displace the car body laterally inrelation to the bogie frame during travel of the trackbound vehicle incurves. Such a member may also be arranged to tilt the car body inrelation to the bogie frame during travel in curves. Furthermore, such amember may be arranged to damp substantially all motions of the car bodyoccurring during the travel of the trackbound vehicle. Such dampingmotions of the car body may be performed both vertically andhorizontally.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, a preferred embodiment of the invention is describedas an example with reference to the attached drawings, in which:

FIG. 1 shows a sectional view of a member according to the presentinvention,

FIG. 2 shows a sectional view of the member in FIG. 1 along the lineA—A,

FIG. 3 shows a member according to the present invention provided todisplace a car body of a trackbound vehicle laterally,

FIG. 4 shows two members according to the present invention provided totilt a car body of a trackbound vehicle.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION

FIGS. 1 and 2 show a member 1 arranged to act between two parts of avehicle which are movable in relation to each other. The member 1comprises a first portion 2 and a second portion 3, which are variablein length in relation to each other in order to influence the positionof the vehicle parts which are movable in relation to each other. Thefirst portion 2 is connectable to one of said vehicle parts by means ofa first ring-shaped member 4 and the second portion 3 is connectable tothe other vehicle part by means of a second ring-shaped member 5. Thefirst portion 2 comprises an elongated rod 6 having external threads 7while the second portion 3 comprises a nut 8 rotatably provided on therod 6. Thereby, the length of the member 1 is variable in an axialdirection L under a rotary motion between the rod 6 and nut 8. Thesecond portion 3 comprises a cylindrical portion 9 having an innercavity arranged to receive an electric rotor machine 10. The electricrotor machine 10 comprises a stator 11, which in a suitable way isrigidly attached in the cylindrical portion 9. The stator 11 comprises aplurality of through windings 12 arranged to conduct an electric currentduring activation of a rotor 13 provided radially internally in thestator 1. The rotor 13 is rigidly connected to the nut 8 so that theyconstitute an integrated part. FIG. 2 shows a sectional view along theline A—A in FIG. 1, this sectional view shows a radial plane, withrespect to the axial direction L, where it is evident that the radialplane extends both through the rotor 13 and the nut 8. The rotor 13shown in the figures surrounds the whole nut 8. The rotor 13 and the nut8 have here a substantially common extension in the axial direction L.The rotor 13 comprises at an external surface four magnets 14, which arearranged to be permanently magnetised. The nut 8, which is integratedwith the rotor 13, comprises internally carried balls 15 which arearranged to run along the external threads 7 of the rod 6 duringrotation of the nut 8. With such balls 15 the friction between the nut 8and the rod 6 may be kept at a very low level. The balls 15 admit also asmaller inclination of the rod 6 in relation to the nut 8 with noconsiderable increase of the friction. In order to obtain asubstantially frictionless rotation of the rotor 13 in the stator 11, afirst bearing 16 and a second bearing 17 are provided.

The electric rotor machine 10, shown in the FIGS. 1 and 2, is asynchronous machine having a permanently magnetised rotor 13. By feedingan alternating current through the windings 12 of the stator 11, is arotating magnetic field formed, the rotation speed of which isdetermined by the frequency of the current and the number of poles. Therotor 13 of a synchronous machine rotates synchronously with therotating magnetic field and the rotor 13 thereby obtains the same speedof rotation as the magnetic field. The rotation speed of the rotor 13may thus be controlled by a variation of the frequency of thealternating current fed through the windings 12 of the stator 11. Withsuch an electric rotor machine 10, it is easy to give the member 1 anecessary control and thereby such properties that is suitable both asdisplacement member and damper member.

FIG. 3 shows a very advantageous application of the electric member 1 ina trackbound vehicle. In this case, the member 1 is arranged to displacethe car body 18 laterally to a desired position during travel of thetrackbound vehicle in curves. The member 1 comprises a first end 2connected to the car body 18 and a second end 3 connected to a bogieframe 19. Since the member 1 is attached between two in relation to eachother resilient parts 18, 19, the member 1 must be able to follow therelative motions between the car body 18 and the bogie 19 without addingstiffness to the spring suspension of the car body 18. A large rotatingmass having a large moment of inertia adds such stiffness to the springsuspension at high frequencies. Therefore, the electric member 1,according to present invention, is very suited to be arranged fordisplacing a car body laterally as it has a very small rotating mass.

FIG. 4 shows another application of the electric member 1 in atrackbound vehicle. Two members 1, according to the above, are each witha first portion 2 connected to a car body 18 and with a second portion 3connected to a bogie frame 19, via a so-called tilting bolster 23. Themember 1 is in this application arranged to tilt the car body 18 inrelation to a bogie frame 19 during travel of the trackbound vehicle incurves. By such a tilting bolster 23, which is resiliently arranged inrelation to the car body 18, the motions of the members 1 do notinfluence the spring suspension of the car body to the same extent andrequirements that the electric member shall have a small rotating massare here not as high as before.

An electric control unit 20 may be arranged to control the electricmembers 1 shown in FIGS. 3 and 4. Such a control unit 20 may be arrangedto sense the lateral acceleration acting on the car body by means of,for example, sensors 21. Therewith, the control unit 20 may calculate anoptimised lateral displacement and tilting of the car body 18 inrelation to the bogie frame 19, during travel in curves, at which thepassengers in the car body 18 experience an optimum of travel comfort.Furthermore, the control unit 20 may sense other parameters necessary todisplace the car body to the optimum position. Such parameters may bethe position of the car body 18, the direction of motion and thevelocity in relation to the bogie frame 19 and be sensed by sensors 22.In the light if this information, the control unit 20 may calculatenecessary values of the current which must be conducted through thestator windings 12 of the respective members 1 in order to displace thecar body 18 from the actual position to the calculated optimum position.Thereafter, the control unit 20 initiates the supply of current,according to calculated values of the current, to each of the statorwindings 12 of the members 1. The respective member 1 is thereby changedin length so that the car body is displaced from the actual position tothe calculated position in relation to the bogie frame 19. Preferably,the supply of current to the windings 12 of the stator 11 is controlledso that the displacement motion of the car body 18 occurs in arelatively gentle way. In the situations, when no lateral accelerationinfluences the car body 18, i.e. on straight stretches, the electricmembers 1 function substantially as damping members for the rotarymotions of the car body 18, which may occur during travel of thevehicle.

The electric members 1, as described above, may with a somewhat simplercontrol unit 20 function only as damping member. The members 1 mayhereby be used both as vertical dampers and horizontal dampers.

The present invention is not in any way restricted to theabove-described embodiment but may be varied freely within the scope ofthe claims. It is, for example, possible to use other types of electricrotor machines than permanently magnetised synchronous machines. Theapplicability of the member 1 is also not restricted to be used intrackbound vehicles but it may be used in substantially all types ofvehicles having two vehicle parts which are movable in relation to eachother.

What is claimed is:
 1. A member arranged to act between two parts of avehicle which are movable in relation to each other, wherein the memberextends between said parts and comprises a first portion connectable tothe first part of the vehicle and a second portion connectable to thesecond part, wherein the first portion comprises an elongated rod havingexternal threads and the second portion comprises a nut rotatablyprovided on the rod so that the length of the member during a rotarymotion between the rod and the nut is variable in an axial direction,wherein an electric rotor machine having a stator and a rotor isarranged to influence said rotary motion and wherein the rotor and thenut are located in relation to each other such that at least one planeperpendicular with respect to the axial direction extends through boththe rotor and the nut, wherein the rotor and the nut are rigidlyconnected and constitute an integrated part.
 2. A member according toclaim 1, wherein the nut comprises internally carried balls arranged torun along the external threads of the rod during the rotary motion ofthe nut.
 3. A member according to claim 1, wherein the stator is rigidlyconnected to the second portion.
 4. A member according to claim 1,wherein the electric rotor machine is arranged to displace said vehicleparts in relation to each other via the member.
 5. A member according toclaim 1, wherein the electric rotor machine is arranged to damp themotion between the vehicle parts via the member.
 6. A member accordingto claim 1, wherein the electric rotor machine comprises a permanentlymagnetized synchronous motor.
 7. A member according to claim 1, whereinthe vehicle is a trackbound vehicle.
 8. A member according to claim 7,wherein said first and second part of the vehicle are a car body and abogie frame.
 9. A member according to claim 8, wherein the member isarranged to displace the car body laterally in relation to the bogieframe.
 10. A member according to claim 8, wherein the member is arrangedto tilt the car body in relation to the bogie frame.
 11. A memberaccording to claim 8, wherein the member is arranged to damp occurringmotions of the car body in relation to the bogie frame.